The present invention relates in general to crash sensing in motor vehicles, and, more specifically, to pressure-based sensing having a pressure chamber location that enables low cost components and avoids negatively impacting other vehicle structures or systems.
Active restraint systems utilize one or more sensors to detect the occurrence of a crash in order to deploy air bags or other restraint or occupant protection devices. Sensor signals are sent to an electronic control module that monitors the signals and determines when conditions warrant activation or deployment of an air bag, for example.
The most commonly used type of sensor is the accelerometer which responds to gravitational forces occurring during deceleration associated with a crash. The accelerometer has a small size, so that it has a minimal effect on the mechanical crash performance of the structures to which it is mounted. In some situations, however, an accelerometer may not perform well because of the nature of the movements of the vehicle structure to which it is mounted both prior to and during a crash. Depending on the transmission of loads, deformation, and other structural issues, certain positions on a vehicle frame wherein an accelerometer might be mounted can be subject to vibrational resonance or other motions that interfere with sensing of the overall vehicle movement. This issue is sometimes addressed by mounting extra struts to the vehicle frame in order to either create an acceptable location for an accelerometer or to modify vibrational resonance in the frame, but such struts may interfere with the intentionally-controlled deformation of vehicle structures during a crash, may be difficult or impossible to package in the available space, or may be too costly. Consequently, other types of crash sensors are also sometimes used.
A different type of known crash sensor directly senses an impact. Examples of impact sensors include a moving ball sensor and a deforming chamber sensor. In a deforming chamber sensor, a pressure or temperature of a fluid (e.g., air) in a chamber being compressed or crushed during a crash can be monitored to detect a deformation. Such impact sensors typically have a greater size, so that it may be even harder to find a good packaging space with sufficient clearance. Known uses of deforming chamber sensors have been especially subject to the problem of the creation of unintended changes in the controlled deformation during a crash.
It would be desirable to provide a pressure-based crash system that 1) does not add strength to the front vehicle frame structure, 2) uses components that can withstand paint oven temperatures without degradation, 3) functions over a wide temperature range, and 4) is easily assembled with low cost components.